How do I know the remaining battery percentage?

You can turn on the “Show Battery Percentage” function within the Tapplock App to check battery percentage.

To view an updated battery percentage of your Tapplock one, you will need to have the lock connected via Bluetooth and the Tapplock App
As an added precaution, if the remaining battery is low, the status indicator will show a blinking red light to remind you of charging after you turn on the lock.